• Piili, Heidi
• Purtonen, Tuomas
• Salminen, Antti

Abstract

Laser welding has an ever growing role in manufacturing technology. Keyhole laser welding is the most important laser welding process in metal industry when exceeding the 1 mm weld penetration. This process uses efficiently the high energy density of a laser beam to vaporize and melt materials, thus producing a keyhole in the material via which the energy is brought to it. The requirements from customer side and the development of new materials have been giving justification for the development of new laser types suitable for material processing with ever higher power values. In contrast, the development of laser technologies has made it possible to build more powerful lasers with excellent beam properties and good electrical efficiency. New laser sources with good absorption and beam quality make the laser welding even more efficient when throughput and efficiency are considered. They show their ability to produce narrower welds with lower line energy. However, the validation of actual keyhole shape, size, and behaviour against the models is still lacking because of the difficulties in performing the measurements of the actual dimensions. It has been shown that the better the beam quality the higher the welding speed. When welding with high power, good beam quality, and wavelength close to 1000 nm, there are some obstacles to overcome, which are caused by high absorption and power density. Typically, problems, such as thermal lensing, can be avoided with proper parameter and tool selection. Typically, the size of the keyhole is according to the focal point size, and the stability of the keyhole plays a major role when considering the ability of the laser welding process to produce high quality welds.

Topics

• density
• impedance spectroscopy
• energy density
• melt